SYNTHESIS AND FUNCTIONALIZATION OF SOME PARA-R-PHENYLIMIDAZO[2,1-B][1,3,4]- THIADIAZOLE DERIVATIVES

The article describes the synthesis of new modifications of derivatives of 6-phenyl-, 6-piodophenyl- and 6-p-bromophenylimidazo[2,1-b][1,3,4]-thiadiazoles - N -((6-(4-iodophenyl)-2-R-imidazo[2,1-b][1,3,4]-thiadiazol-5-yl)methyl)-alkyl/ heterylamine based on the Mannich reaction, bromination 2((ethylsulfonyl)methyl)-6-phenylimidazo[2,1-b][1,3,4]-thiadiazole and the structure of the resulting compounds was established on the basis of IR spectroscopy. It was shown that the presence of substituents at the 2-nd position of the thiadiazole fragment and substituents at the 5th and 6th positions of the imidazole fragment of this heterocycle cause the appearance of a nonequivalent absorption band in the imidazo-thiadiazole fragment.

Biomimetic Non-Heme Iron-Catalyzed Epoxidation of Challenging Terminal Alkenes Using Aqueous H2O2 as an Environmentally Friendly Oxidant

Catalysis mediated by iron complexes is emerging as an eco-friendly and inexpensive option in comparison to traditional metal catalysis. The epoxidation of alkenes constitutes an attractive application of iron(III) catalysis, in which terminal olefins are challenging substrates. Herein, we describe our study on the design of biomimetic non-heme ligands for the in situ generation of iron(III) complexes and their evaluation as potential catalysts in epoxidation of terminal olefins. Since it is well-known that active sites of oxidases might involve imidazole fragment of histidine, various simple imidazole derivatives (seven compounds) were initially evaluated in order to find the best reaction conditions and to develop, subsequently, more elaborated amino acid-derived peptide-like chiral ligands (10 derivatives) for enantioselective epoxidations.

Novel (2-amino-4-arylimidazolyl)propanoic acids and pyrrolo[1,2-c]imidazoles via the domino reactions of 2-amino-4-arylimidazoles with carbonyl and methylene active compounds

The unexpectedly uncatalyzed reaction between 2-amino-4-arylimidazoles, aromatic aldehydes and Meldrum’s acid has selectively led to the corresponding Knoevenagel–Michael adducts containing a free amino group in the imidazole fragment. The adducts derived from Meldrum’s acid have been smoothly converted into 1,7-diaryl-3-amino-6,7-dihydro-5H-pyrrolo[1,2-c]imidazol-5-ones and 3-(2-amino-4-aryl-1H-imidazol-5-yl)-3-arylpropanoic acids. The interaction of 2-amino-4-arylimidazoles with aromatic aldehydes or isatins and acyclic methylene active compounds has led to the formation of pyrrolo[1,2-c]imidazole-6-carbonitriles, pyrrolo[1,2-с]imidazole-6-carboxylates and spiro[indoline-3,7'-pyrrolo[1,2-c]imidazoles], which can be considered as the analogues of both 3,3’-spirooxindole and 2-aminoimidazole marine sponge alkaloids.

THEORETICAL STUDY OF NUCLEOSIDE5´-PHOSPHORAZOLIDE-2´,3´-CYCLO(THIO)CARBONATE FORMATION POSSIBILITY IN REACTION OF NUCLEOTIDES AND N,N´-ACYLBISAZOLES BY QUANTUM-CHEMICAL METHODS

Nucleoside-5´-phosphates and N,N´-(thio)carbonylbisazoles interaction was studied for the evaluation of nucleoside-5´-phosphorazolide-2´,3´cyclo(thio)carbonate formation possibility by the semi-empirical method PM6 of SCIGRESS Modeling 3.0.0 software. Azole moiety involves imidazole fragment. It was shown that formation of nucleoside-5´-phosphorazolide2´,3´-cyclo(thio)carbonates is energetically less efficient than formation of nucleotide-5´-phosphorazolides.

How important is thermal expansion for predicting molecular crystal structures and thermochemistry at finite temperatures?

Molecular crystals expand appreciably upon heating due to both zero-point and thermal vibrational motion, yet this expansion is often neglected in molecular crystal modeling studies. Here, a quasi-harmonic approximation is coupled with fragment-based hybrid many-body interaction calculations to predict thermal expansion and finite-temperature thermochemical properties in crystalline carbon dioxide, ice Ih, acetic acid and imidazole. Fragment-based second-order Möller–Plesset perturbation theory (MP2) and coupled cluster theory with singles, doubles and perturbative triples [CCSD(T)] predict the thermal expansion and the temperature dependence of the enthalpies, entropies and Gibbs free energies of sublimation in good agreement with experiment. The errors introduced by neglecting thermal expansion in the enthalpy and entropy cancel somewhat in the Gibbs free energy. The resulting ∼ 1–2 kJ mol−1errors in the free energy near room temperature are comparable to or smaller than the errors expected from the electronic structure treatment, but they may be sufficiently large to affect free-energy rankings among energetically close polymorphs.

Crystal structure of tetraaqua[2-(pyridin-2-yl)-1H-imidazole-κ2N2,N3]iron(II) sulfate

In the title compound, [Fe(C8H7N3)(H2O)4]SO4, the central FeIIion is octahedrally coordinated by two N atoms from the bidentate 2-(pyridin-2-yl)-1H-imidazole ligand and by four O atoms of the aqua ligands. The largest deviation from the ideal octahedral geometry is reflected by the small N—Fe—N bite angle of 76.0 (1)°. The Fe—N coordination bonds have markedly different lengths [2.1361 (17) and 2.243 (2) Å], with the shorter one to the pyrimidine N atom. The four Fe—O coordination bond lengths vary from 2.1191 (18) to 2.1340 (17) Å. In the crystal, the cations and anions are arranged by means of medium-strength O—H...O hydrogen bonds into layers parallel to theabplane. Neighbouring layers further interconnect by N—H...O hydrogen bonds involving the imidazole fragment as donor group to one sulfate O atom as an acceptor. The resulting three-dimensional network is consolidated by C—H...O, C—H...π and π–π interactions.